Let Φn(X) and Ψn(X)=Φn(X)Xn−1 be the n-th cyclotomic and inverse cyclotomic polynomials respectively. In this short note, for any pair of divisors d1=d2 of n, and integers l1 and l2 such that 0≤l1≤φ(d1)−1 and 0≤l2≤φ(d2)−1, we show that ⟨Xl1Ψd1(X)(1+Xd1+…Xn−d1),Xl2Ψd2(X)(1+Xd2+…Xn−d2)⟩=0, where ⟨⋅,⋅⟩ is the inner product on Q[X] defined by ⟨∑kakXk,∑kbkXk⟩=∑kakbk.